Example of a test of an industrial, non-aeronautic character. This type of visualization complements wind tunnel tests on
structures placed in the wind (tower buildings, chimney stacks, street lamps, etc.). Near the ground one can see the horseshoe
vortex already observed in Image 2. This mounting also permits the simulation of the smoke plume
emitted by a chimney and the study of its expansion (pollution problem).

Image created by Henri Werlé. Reproduced with permission from his spectacular
collection Courants et Couleurs published in 1974 by ONERA, the French Aerospace Lab.